ELECTROSTATIC-BASED PESTICIDE SPRAY SYSTEMS .1. A THEORETICAL INVESTIGATION

In this paper a theoretical investigation of electrostatic-based pesti cide spray systems is carried out. Owing to the complexity of the prob lem, the system was divided into two different regions, one inside the nozzle, and the other between the nozzle and the target. Two mathemat ical models for the two regions have been developed and a charge simul ation method (CSM) is used. Inside the nozzle particular emphasis is l aid on the effect of the voltage applied to an electrostatic induction spray nozzle on the droplet's charge, mobility and charge-to-mass rat io. The variation of these parameters along the jet is also predicted by the model. In addition, the model takes into consideration the effe ct of applied voltage on both spray current and charge density at the nozzle. Results show that, inside the nozzle, the volume charge densit y of the droplets, the spray current and the droplet's charge and char ge-to-mass ratio do increase with applied voltage. In the region betwe en nozzle and target, the analysis focuses on studying the spatial dis tribution of the droplet's charge density, travel time and trajectory. In this model, the charge density, previously calculated at the nozzl e, is taken as a variable parameter. A csm approach is combined with t he method of characteristics to solve Poisson and current density equa tions subject to the validity of the current continuity condition. In this region, the model clearly indicates that the droplet's trajectory depends on the spatial distribution of the droplet charge density and the air flow velocity. The travel time between the nozzle and the tar get is also calculated. Curves illustrating the results are shown and explanations provided.